This invention relates to air sampling and more particularly to an improved hand-operable, portable vapor sampling probe for collecting vapors of specific compounds present in the air or on surfaces.
One method of detecting certain compounds such as explosives involves vapor sampling followed by analysis of the sampled vapors. For example, G. E. Spangler et al. in their paper "Analysis of Explosives and Explosives Residues With Ion Mobility Spectrometry (IMS)" included in the Proceedings of the International Symposium on the Analysis and Detection of Explosives March 29-31, 1983, FBI Academy, Quantico, Virginia, disclose a surface sampler closely coupled to a hand-held ion mobility spectrometer (IMS). The surface sampler includes a conical inlet which may be placed near a surface and in which are mounted a tungsten halogen lamp to heat the surface and air jet nozzles to cause turbulence in the conical inlet. A sample released from the surface swirls up transport lines to the IMS for detection.
Another form of vapor sampling equipment, described in the 1983 paper of D. F. Wardleworth et al. entitled "A Novel Method For the Recovery of Volatile Explosives Traces", is a contact heater including a spring-loaded platen with a hole through which air is drawn by a pump for collection of vapors such as explosives in a Tenax absorbent trap. The contact heater is heated to about 100.degree. C. and kept in contact with a sample surface for 2-5 minutes while vapors are collected. Later the vapors are eluted from the absorbent trap with ethyl acetate and analyzed by gas chromatography or mass spectroscopy.
For maximum effectiveness and versatility a vapor sampler must fulfill several requirements. It should permit acquisition of samples both from surfaces and from open areas (i.e., areas remote from surfaces which may contain the source of such vapors). The vapor sampler should be lightweight, portable, and easy to operate and aim at a specific target. It should collect samples rapidly and without damaging the sampling surface or altering the vapors in a manner which interferes with their analysis. If the collected vapors are to be analyzed in a separate apparatus, the vapor sampler must also facilitate rapid transfer of collected vapors to the vapor analyzer.
Accordingly, it is an object of the invention to provide an improved sampling probe for rapidly collecting vapors of selected compounds such as explosives or the drugs cocaine and heroin.
It is an object of the invention to provide a portable vapor-sampling probe for collecting vapors from surfaces and which controls the flow of air over a target portion of a sampling surface.
An object of the invention is to provide a portable, battery-operable vapor-sampling probe capable of heating a target portion of a sampling surface and preventing overheating of the target.
It is an object of the invention to provide a portable vapor-collecting probe which facilitates rapid transfer of vapors from a collector to a vapor analyzer.
It is a particular object of the invention to provide a portable vapor sampling probe which draws a sample into its collector in a manner such that essentially all air in the sample passes over a heated target portion of the surface.